Revert of [package.proto] convert deps from list to map.

Revert of [package.proto] convert deps from list to map. (patchset #3 id:40001 of https://codereview.chromium.org/2779683005/ )

Reason for revert:
Prepping revert <just in case>

Original issue's description:
> [package.proto] convert deps from list to map.
> 
> This is a backwards-incompatible proto change, but this CL makes the engine
> compatible with BOTH versions (simultaneously :)).
> 
> Files handled by e.g. the autoroller code are 'sticky'. If they were
> version 1, they'll be written as version 1. If they were version 2, they'll
> be written as version 2.
> 
> Once version 2 is in use everywhere, I will remove support for version 1.
> 
> R=dnj@chromium.org, nodir@chromium.rog, phajdan.jr@chromium.org
> BUG=
> 
> Review-Url: https://codereview.chromium.org/2779683005
> Committed: https://github.com/luci/recipes-py/commit/4fcdb75517198a9ca32c7c4aecbe2e6f54b8b6c2

TBR=dnj@chromium.org,nodir@chromium.org,phajdan.jr@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

[iannucci, 2017-03-28 16:16:42]

Created Revert of [package.proto] convert deps from list to map.

[iannucci, 2017-03-28 16:17:15]

This is just in case it looks like it goes sideways.

[iannucci, 2017-03-28 16:42:21]

woohoo! not needed